Field of the Invention
The present invention relates to an element substrate and a printhead, and particularly to, for example, a printhead that incorporates an element substrate with a temperature detection element which detects an ink discharge status.
Description of the Related Art
In a printing apparatus using an inkjet printhead (to be referred to as a printhead hereinafter), a foreign substance may clog an ink orifice (to be referred to as an orifice hereinafter), or a bubble entering into an ink supply channel may clog the supply channel. If this occurs, an ink discharge failure (to be referred to as a discharge failure) from the printhead is caused. In particular, a printing apparatus that prints by using a full-line printhead which supports the full width of a print medium and includes a number of orifices arranged in a line can print at high speed, and thus a process for the discharge failure also needs to be performed at high speed. More specifically, in the printing apparatus that uses the full-line printhead, it is very important that an orifice (discharge nozzle) which causes the discharge failure is specified at high speed, and complimentary printing and an ink discharge recovery operation are performed.
Conventionally, various techniques to solve such a discharge failure have been proposed.
Japanese Patent Laid-Open No. 2007-290361 discloses an element substrate on which a plurality of heaters which generate heat energy for discharging ink from orifices are formed on a silicon (Si) base, and a temperature detection element of a thin film is formed via an interlayer insulation film immediately below each heater. According to Japanese Patent Laid-Open No. 2007-290361, a temperature detection circuit detects temperature information from the respective temperature detection elements and determines, by a difference between a temperature change by a discharge failure and a temperature change when ink is discharged normally, whether ink discharge is normal or suffers from the discharge failure.
The temperature detection elements described in Japanese Patent Laid-Open No. 2007-290361 adopt an arrangement for detecting a small temperature change precisely. FIG. 12 is a layout diagram showing the positional relationship between conventional heaters and temperature detection elements. As shown in FIG. 12, each temperature detection element 3 is folded a plurality of times and arranged immediately below a corresponding one of heaters 5, setting a resistance value high. In this arrangement, in order to increase the resistance value of each temperature detection element 3, it is effective to make, thin and long, the line width of the temperature detection element arranged immediately below the corresponding one of the heaters 5.
However, an area occupied by each heater is restricted, and the size of a corresponding one of the temperature detection elements that can be arranged under that restriction is restricted, as a matter of course. It is therefore difficult to further increase the resistance value of each temperature detection element 3 in order to improve the sensitivity of the temperature detection element 3.